(a) Field of the Invention
The present invention relates to a mode control apparatus of a hybrid vehicle. More particularly, when a driving mode is converted from an electric vehicle (EV) mode to a hybrid electric vehicle (HEV) mode, the driving mode is converted using slip of a dual clutch. An engine clutch can be designed as a dry clutch to reduce production cost.
(b) Description of the Related Art
A hybrid vehicle is a vehicle that uses at least two power sources. Generally, the hybrid vehicle is operated by an engine and a motor. The hybrid electric vehicle can be manufactured in various types using the engine and the motor. FIG. 1 is an exemplary schematic diagram illustrating a parallel hybrid vehicle according to the related art. As shown in FIG. 1, in the parallel hybrid vehicle, an engine 10 and a motor 30 are connected by an engine 10 clutch, a dual clutch 40 is connected to shafts of the engine 10 and the motor 30, and a transmission 50 is connected to the dual clutch 40. A hybrid start generator (HSG) 12 is provided in the engine 10.
Driving modes of the hybrid vehicle may be an EV mode which is a mode of a true electric vehicle using power of the driving motor 30, an HEV mode using torque of the driving motor 30 as auxiliary power while using torque of the engine 10 as main power, and a regenerative braking (RB) mode collecting brake and inertia energy through generation of the driving motor 30 to charge the battery during braking or driving using inertia of the vehicle.
A transition between the EV mode and the HEV mode is one of key features of the hybrid vehicle, and affects driving performance, fuel consumption, and power performance of the hybrid vehicle. Generally, in initial starting, the hybrid vehicle operates the motor 30 using power charged in the battery, wherein the dual clutch 40 is locked up by a driving torque generated at the motor 30, and the driving torque is transmitted to a drive shaft 60.
However, it is necessary to convert a driving mode to the HEV mode when the hybrid vehicle is driven in the EV mode in a low speed region. The low speed region may be one in which the motor speed and engine speed cannot be synchronized since the motor speed is less than a minimum engine speed. For example, the driving mode needs to be converted from the EV mode to the HEV mode when the vehicle travels on a steep uphill road (e.g., travels on an incline) while the vehicle is driving on a planar road (e.g., a substantially even road with minimal inclines or declines) in the EV mode, when the vehicle drives on a long uphill road, or when the vehicle starts in EV mode but power of the engine is necessary before the motor speed reaches a synchronizing speed of the engine.
However, according to the related art, excessive heat is generated in an engine clutch 20, since power of the engine 10 is transferred through slip of the engine clutch 20. Therefore, the engine clutch 20 should be designed as a dry clutch rather than a wet clutch. Accordingly, when the engine clutch 20 is designed as a wet clutch, manufacturing cost is increased and fuel consumption is deteriorated. Further, since the mode change is performed through slip of the engine clutch 20, slip capacity of the engine clutch 20 should be increased. Since a friction area of the engine clutch 20 is increased, degree of design freedom may be deteriorated.
The above information disclosed in this section is merely for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.